Naruto "changed" more than Luffy.
Yet Luffy is a better written, more rounded, and more consistent character. Because Oda kept his character consistent, concise, and simple.
Naruto's character-changes aren't naturally part of his character. They are forced into the bigger narrative just because. Why does he want to go after Sasuke? Who the fuck knows.
If he was written by a better writer who actually understood the character more, then he would have been.
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Except Vergo had a pretty damn impactful scene with Doflamingo right when he was about to be "killed". A scene that really sold the fact that Doflamingo isn't a heartless one-note character, but someone with personal history, and relationships. A subtle touch that elevates Vergo.
Lucci, on the other hand, has...................
Naruto became obnoxious during the later parts, but his obsession with Sasuke was pretty typical "I'll never give up on a friend" And while yes, Kishimoto did not devote nearly enough time to show their "freindship", you have to remember that Naruto literally had no friends at that point of the story - Sakura and Sasuke were among the first people he interacted with so I can understand why Naruto didn't want to give up on him. I'm more mad with how they made Naruto more preachy by the end of the series.
That being said, Luffy has his faults too. Sometimes I feel his character arc is a little too static. Simple is fine, but I do wish Luffy showed a little more maturity when it comes to certain things. Not everything since we still want him to be Luffy, but just certain things. OP is really long, so I get why people sometimes get annoyed with Luffy's lack of progression character wise.